1. Field of the Invention
The present invention relates to an optical fiber based communications network, and more particularly to an optical switch arrangement that provides increased use of the deflection angle capability for each mirror in an array of optical switching mirrors.
2. Discussion of the Related Art
In recent years, internet usage and other computer communications modes have become widespread. Moreover, audio and video applications that are becoming increasingly popular require large amounts of information (bandwidth) to be transferred. As a result, demands on the bandwidth supported by communications systems have skyrocketed. Optical communication systems have become increasingly important to fulfill such needs.
Such optical communications systems are capable of rapidly transferring large volumes of information by converting electrical signals into light signals and transmitting the light through optical fibers. The optical fibers form a network of optical paths between different geographic locations (e.g., different metropolitan areas). To route the information between the different locations, the information is switched between different optical paths. Conventionally, the information is switched by converting the optical signals into electrical signals, switching the electrical signals, reconverting the electrical signals to optical signals and re-transmitting the optical signals onto the desired optical path.
With advances in optical communications technology, optical switches (such as micro-mirror switches) are being developed to provide large switching fabrics that operate in the optical domain and can switch more information faster than electrical switches. Input and output coupling may be achieved by aligning an optical fiber, a collimating lens arrangement, and the mirror chip at both the inputs and the outputs.
Moreover, applications involving long distance optical paths at high bit rates ( greater than Gbs) require the use of optical fibers requiring having tight fabrication tolerances to avoid optical loss if strict angular tolerances (within 0.01 degrees) are not achieved. In addition, such optical fibers have a small core diameter and a small numerical aperture. The small numerical aperture implies that the cone of light that can be accepted by the optical fiber is narrow. Hence, for reasons such as these, through-put is easily decreased if the light is not properly focused or if the light is diminished in intensity, thereby potentially causing signal loss or signal deterioration.
To successfully operate optical switches, the mirrors must be precisely aligned and the distance between mirrors reflecting a beam to connect fibers should be minimized. If the angular position of the steerable mirrors is off and/or if the mirrors are too far apart, some or all of the light from the input fiber will not reach the selected output fiber. There remains a need in the art for an optical switch having a compact and reliable arrangement of steerable mirrors.
Accordingly, the present invention is directed to an optical switch that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An objective of the present invention is to provide increased use of the full deflection angle capability for each mirror in an array of optical switching mirrors.
Another objective of the present invention is to reduce optical losses by shortening the distance between the inputs and the outputs of an optical switch.
Another objective of the present invention is to reduce optical losses by focusing reflected signals between mirrors to minimize beam spreading caused by diffraction.
Another objective of the present invention is to reduce optical losses caused by aberrations in a lens system positioned between mirror arrays in an optical switch.
Additional features and advantages of the invention will be set forth in the description, which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an optical switch includes a first mirror array; a second mirror array; optical inputs substantially aligned with the first mirror array; optical outputs substantially aligned with the second mirror array; a lens system positioned between the first and second mirror arrays; and wherein the second mirror array is located substantially along a focal plane of the lens system
Another aspect is an optical switch including a lens system having a first side, a second side and a centerline going through a central portion of the first and second side; a first mirror array positioned on the first side of the lens system; a second mirror array having a centerline and positioned on the second side of the lens system; optical outputs aligned with the second mirror array; optical inputs positioned on the first side of the lens system and aligned with the first mirror array; and wherein the centerline of the second mirror array and the centerline of the lens system are on the same axis.
Another aspect is an optical switch including a a lens system having a first side and a second side; a first mirror array positioned on the first side of the lens system; a second mirror array positioned on the second side of the lens system along a focal plane of the lens system and substantially perpendicular to an optical axis of the lens system; and a third mirror array positioned on the first side of the lens.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.